关键词: 悬沙输运; 半日潮流输沙; 余流输沙; M4潮流输沙; 空间结构特征; 准调和分析; 北港; 长江口;

Abstract: The Yangtze Estuary is multi-braided river mouth with medium tide characteristics.As a second-grade channel to the sea in Yangtze Estuary,the north channel is planned as an important navigation channel,so the study on its sediment transport law and process has significant meanings.To examine the spatial structure of suspended sediment transport and the contribution mechanism of each driven factor in the north channel,the observation data of tidal current and sediment concentration over five points during spring tide in a cross-section of the channel were decomposed into mean components and several tidal fluctuations based on harmonic analysis.The research results showed that the sediment transport in the study cross section was mainly contributed by residual transport,semi-diurnal tidal transport and M4 tidal transport,and each of them significantly varied over the cross section.The total transport is directed to the outer sea in most section,while only a small part of the southern section showed an upstream transport.The seaward transport in the northern section was mainly driven by the strong discharge induced residual flow.The M2tidal transport in the northern concave bank was significantly stronger during ebb period than that during flood period under the influence of runoff and slightly channel curvature,resulting in a seaward M2tidal transport in the northern transect,which is an major contribution factor only less than the residual transport.The transport in the southern cross section was mainly contributed by M2 tidal transport and M4 tidal transport,in which the former component dominated.The cross-sectional characteristics of sediment concentration and the structural of sediment discharge are closely related to the underwater landform structure and the evolution trend of erosion and deposition in the north channel.

Key words: suspended sediment transport; semi-diurnal tidal transport; residual transport; M4 tidal transport; quasi-harmonic analysis; north channel; Yangtze Estuary;